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Can a pilot with an ICAO Multi-Crew Pilot License fly an airliner into the U.S.?
In the question How do non-US pilots get the hours necessary for an ATP?, the question was raised of whether we have 250 or 500 hour foreign pilots flying airliners into major U.S. airports. DeltaLima's answer mentioned the ICAO Multi-Crew Pilot License (MPL), which

allows a pilot to exercise the privileges of a co-pilot in a commercial air transportation on multi-crew aeroplanes.

Of particular interest is the large gap in the minimum experience requirement between this license and an ATP license that would normally be required to fly an airliner in the U.S. While the FAA normally requires airline pilots to have at least 1,000 flight hours (or 1,500 if they don't have a degree in aviation,) the requirement for the ICAO MPL standard is much less. According to ICAO:

The ICAO Standard for the MPL specifies 240 hours as the minimum number of actual and simulated flight hours performing the functions of the pilot flying and the pilot non-flying.

While the U.S. has no such pilot certificate, what I'm wondering is:

Is a pilot who receives an MPL from another country allowed by the FAA to fly an airliner on normal scheduled passenger service routes into major U.S. airports?
If so, are there any further restrictions on doing so? For instance:

Can they fly a route subject to ETOPS regulations into the U.S.?
Can they fly a 777 into the U.S. or are they limited to smaller aircraft (e.g. turboprops and the like?)

What is required for a pilot to fly in another country? and I have a European EASA license - what do I need to do to be allowed to fly in the US? cover some general points about the certification requirements to fly an aircraft in a country other than the one where the pilot obtained their license, but they don't address issues specific to flying airline routes.
Interestingly, ICAO seems to suggest that pilots with an MPL would indeed be able to fly in the right seat of an airliner into any ICAO country:

International recognition of flight crew licenses
The Convention on International Civil Aviation, often called the Chicago Convention, provides for worldwide recognition of flight crew licences issued by any member State of the International Civil Aviation Organization (ICAO) provided that:

1.the licence meets or exceeds the ICAO licensing Standards of Annex 1 – Personnel Licensing to the Convention on International Civil Aviation; and
2.the licence is used on an aircraft which is registered in the State which has issued or validated the licence.

If the licence is to be used on an aircraft which is not registered in the issuing State, the licence holder must obtain a validation of the licence from the State of Registry or alternatively obtain a new licence issued by the State of Registry.

Can someone provide a reference to the FARs (or something of similar authority) or cite personal experience to confirm whether this is indeed allowed and, if so, what restrictions are placed on such operations?

an emergency is all it takes

@ratchetfreak Well I suppose you could answer that to just about any question that starts with "Can a pilot...", but that's not really what I'm asking about here. I'm wondering whether someone with an MPL (according to the ICAO standard) could fly SIC on a regularly-scheduled airline flight into the U.S. (which has no such thing as an MPL,) not whether they could divert to the U.S. in an emergency situation.

The questions you linked to deal with operating aircraft registered in the destination country. While the ICAO rule you quote covers flying aircraft registered in your country. So those pilots can fly to and from US with aircraft registered in their countries, but not fly aircraft registered in the USA.

If your license and registration are from the same country, then that country's licensing rules apply in any ICAO member state that you fly to, rather than those of the country you're in.  It's only when you mix countries that things get weird.

The MPL doesn't allow the holder to fly as Pilot-in-Command, although in a pinch he probably could do it.  It's a basic ticket to allow a non-ATPL pilot to fly as a fully qualified crew-member of an aircraft that otherwise requires the full ATPL ticket.  Elsewhere the pilot would likely be accumulating only solo experience, and he won't be much use when transitioning to a multi-crew airplane.  The MPL only allows the holder to act as copilot, 2nd officer (flight engineer) or cruise pilot, not as PIC, on any flight including to the USA. Where it's used, the MPL holder will be granted his ATPL when he completes any additional regulatory requirements and has accumulated the required hours. The MPL pilot is entitled to fly in his aircraft as co-pilot from anywhere outside the USA into the USA, although not in a USA-registered aircraft. Some pilots start their MPL training after completing A PPL or CPL beforehand.

I thought MPLs do not have a CPL

Yes, mostly they don't. A CPL is not required, but some MPLs start their training with a PPL or CPL in hand already.  I edited my answer to make clear that MPLs don't always have a CPL (nor an Instrument Rating).

Yes. Remarkable to think that the FAA permits the foreign-operated airplane off your wingtip on a simultaneous approach into JFK to have a MPL FO with as little as 258 hours (8 hours gained while on current flight) while the same FAA requires 1500 hours for the FO in your U.S. operated airplane of the same type.
Note the odd situation when your initial training is for multi-crew ops: Per ICAO, MPL is equivalent to CPL endorsed with an instrument rating and a type rating on a multi-crew aircraft. But ... an MPL pilot cannot generally fly a single pilot aeroplane without meeting additional requirements. (!) IDK what happens if the Captain becomes incapacitated during a flight with a MPL FO.
The Ethiopian 737 MAX that crashed March 2019 had a MPL FO with a total of 361 hours. He had 207 hours in type, all of them accrued within the 90 days prior to the accident but was certified to fly as a 737 FO 88 days prior to the accident. (?!)
The Final Report of the Lion Air 737 MAX crash investigation noted that in establishing the pilot type rating, training, checking and currency requirements for a new airplane, Boeing uses a group of pilots who have an operational flying background, and the group includes airline line pilots "to help ensure the requirements are operationally representative." The Safety Recommendation: "The FAA and OEMs should re-evaluate their assumptions for what constitutes an average flight crew’s basic skill and what level of systems knowledge a ‘properly trained average flight crew’ has when encountering failures."
My thoughts: The FAA should add to their intrepid Glossary of terms: Properly Trained Average Flight Crew — The lowest common denominator of pilot competency found in the worldwide pilot pool; used as the best case design standard for human factors.
==========================
14 CFR Part 129 — OPERATIONS: FOREIGN AIR CARRIERS AND FOREIGN OPERATORS OF U.S.-REGISTERED AIRCRAFT ENGAGED IN COMMON CARRIAGE
§ 129.15  Flightcrew member certificates
Each person acting as a flightcrew member must hold a certificate or license that shows the person's ability to perform duties in connection with the operation of the aircraft. The certificate or license must have been issued or rendered valid by:
(a) The State in which the aircraft is registered; or
(b) The State of the Operator, provided that the State of the Operator and the State of Registry have entered into an agreement under Article 83bis of the Convention on International Civil Aviation that covers the aircraft.
==========================

Many remarkable thing have come to light during the would be a farce if people had not died MAX cerification process.

A farce is a farce. The fact that people died and will continue to die if the cause—inadequate training, which is a clear and present danger—is not addressed and eliminated, makes the media’s interference in the investigative process criminal. The ICAO needs to analyze the decade+ worth of real life experience since the MPL was created and evaluate how it serves the flying public in contrast to the FAA’s 1500 hr restriction that was initiated at the same time.

I agree. It makes me wonder how planes get more an more complicated, yet at the same time there is a tendency to create licence categories that enable less and less trained people to fly these winged computers. Still, Boeing had a key role in the MAX catastrophy. They tried to avoid having to train pilots! Stupid, stupid, stupid.

@PeteP. Yeah, it's especially interesting to compare vs. the U.S. in that same period. On all U.S. air carriers put together (which represent a rather large percentage of all air scheduled air carrier operations worldwide,) there has been exactly 1 passenger death since 2009. And that was due to flying debris from an engine failure. The last passenger fatality due to pilot error was the Colgan crash in 2009 and the last one on a mainline airliner was the A300 crash in Queens in 2001, nearly 19 years ago.

@jpe61 Avoiding training i.e. designing for natural human behavior/capability is not a bad objective. Training often tries to overcome natural behavior/capacity but when the human brain is sufficiently fatigued or overstressed it tends to revert to a minimal effort mode, perhaps in self-protection. Then pilots recall the most easily recalled muscle memory and perform actions for airplane B while flying airplane A. That reversion point is unpredictable due to the number of factors involved and individual variances in response to each. The same type rating is not to save money but for safety.

@jpe61 Got carried away and forgot to point out that no simulator training was/is possible for MCAS; it has no ON/OFF switch, no handles, knobs or levers by which its operation can be modulated. No warnings, messages or procedures that mention it. Normal operation is not noticeable except as  a spinning trim wheel which cannot be discerned from operation of the Speed Trim System. Non-normal operation manifests as a runaway stab trim, the procedure for which is taught for the basic 737 type rating. Sim training for MCAS = teaching a driver to shift gears in an automatic transmission car.

@PeteP. The whole shitshow was designed such that pilot interaction was nonexistent. Unmanageabe, untrainable. Training was not necessary, since it was impossible, as you mentioned.

A pilot with an MPL licence here. I've been flying in and out of the US for the past year with an MPL licence. In all fairness I've been flying around the rest of the world and amassed 2000hrs before I flew to the US for the first time.


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Is it possible to maintain horizontal flight with the angle of attack above critical value by increasing speed?
In this video a stall happens at 1:40 upon reaching the critical angle of attack. The air flow is now detached from the upper part of the wing, resulting in higher pressure above the upper part of the wing, thus eliminating the major factor of lift.

Let's imagine that we have extremely powerful engines and enough tail stabilizer authority to maintain horizontal flight with any speed.
Is it possible to maintain horizontal flight when:

wings have high angle of incidence (let's assume some experimental design)*
aircraft has zero pitch condition (straight and level flight)
permanent state of high angle of attack (as the consequence of the 1 and 2)

*high angle of incidence is an angle between wing chord and longitudinal axis of the plane (fuselage)
I assume, the lift that we will get in this case, will be generated mostly by Newton's law by deflecting air ONLY by the LOWER side of the wing.

Given your edit, I feel like the only answer can be "given a big enough engine, even a brick can fly"

Please see the McDonald-Douglas F-4 for further details.

That is kind of what the mechanism of lift of a flat plate does: the sharp leading edge destroys the upper flow pattern almost immediately. This question has more info on it.
The lower side of the wing does provide as much or more lift, even when stalled, at AoA of 45°, so lift would not be the problem. Drag would be:
Image source
On this scale, drag for the NACA 0012 profile is very close to zero until the aerofoil stalls, after which it jumps up and continues climbing. At AoA of 45° the C$_D$ is 1.1 instead of about 0.02 when not stalled - you need over 50 times the thrust to maintain the stalled condition you are describing!

I fly a plane that doesn't stall... With power and half flaps, you pull the stick gradually and the plane ends up with its longitudinal axis almost vertical. One can't stay that way for long, because the engine can't have adequate lubrication in that position and –besides– the prop can't keep the altitude, so it starts to fall tail first...
But it doesn't stall... It's a STOL single-engine 'Savannah', an Italian clone of the Zenith CH701...

@Koyovis, Thanks, I understand that there's will be lot's of drag and the thrust requirements is much higher. What kind of speed increase is needed to maintain horizontal flight in this condition? (assuming the wing area stays the same).

If you mean a horizontal flight path - same speed as just before the stall, but at an angle of attack of 45 degrees.

What you are describing is what is known as "Coffin Corner". It is the part of the flight envelope where neither engine power nor angle of attack can prevent a stall. The aircraft enters what we call the 'fall down go boom' mode of flight.

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Why do missiles typically have cylindrical fuselage and not a fuselage that generates more lift?
For example, Tomahawk Cruise Missile, or Harpoon anti-ship missile. They fly straight and level for the most part of their flight regime. I think if they had a fuselage optimised for level flight then they could have a greater range. Something of a lifting-fuselage.
I know that even their cylindrical body generates lift at some angle of attack but it comes at the expense of drag, so a more optimised shape could result in a greater L/D ratio and hence a longer range.
I think that space and volume constraints may be an issue, like a circular cross section probably has the largest volume to store whatever.

These missiles are nowhere near comparable. The AMRAAM flies at Mach 4 while the Tomahawk is subsonic. The former is unlikely to benefit from lots of extra drag in exchange for some additional lift in horizontal flight, while it might make sense for the latter. Consider narrowing your question down.

I suppose that some missiles spin around their axis to augment their stability, just like a bullet. A cylindrical shape makes in that case sense.

ease of construction, and thus cost considerations no doubt come into play. The ALCM is triangular mostly because it was designed for packing on a rotary launcher, and a triangular shape allows for more missiles to be packed on that so the shape made sense there, not for aerodynamic reasons.

Once you reach the point of having "enough lift", there's no benefit to "more lift".  Instead, the design focus becomes "less drag".

@Mark I think a cylindrical fuselage creates lift by being at certain AoA all the time, if the fuselage created more lift then it could be at lower AoA and create less drag. What do you think?

@TonyStark, I think that a fuselage at zero AoA will generate less drag than one at a non-zero AoA.

I don't know how much of a contributing factor this is, but some (maybe most or all) big munitions need to be periodically rotated while stored to prevent the composition of their propellants and explosives settling into layers. Easier to build racks that allow this if they're cylindrical.

Not only round, but they also need to be pointy at the top or they will just bounce back to from where it was launched.

@winny damn! Admiral General Aladeen was onto something

Rockets with solid fuel must be round, or they would weigh more. Remember that the rear part is filled with fuel which gradually burns away, so the whole fuel container has to withstand the pressure which in the end propels the missile. Only a cylindrical body will do this efficiently. Depending on the routing of cables and the position of actuators, the aeroshell (the outer skin that defines the body of the missile) can be different from the casing of the rocket motor, however, structural efficiency favors to have a cylindrical body.
The throat of the rocket nozzle allows to position the actuators of the rear surfaces within the cylindrical contour and sometimes you will see a cable conduit running along the outside of an otherwise cylindrical fuselage.
For the turbojet-propelled missiles: their body shape is determined by their storage. Submarine-launched cruise missiles have the same diameter as a torpedo, for very practical reasons: They are meant to be launched from torpedo tubes.
Air-launched cruise missiles which are stored on rotary launchers have a rounded trapezoidal cross section, so more of them can be stored in a constrained space.
Regarding the myth of the efficiency-enhancing lift-producing fuselage: This has been laid to rest for more than half a century by now. What counts is the lift-to-drag ratio and producing lift is trivial when the minimal speed during your mission is somewhere around Mach 0.5.
At high dynamic pressure everything will produce ample lift. Now the goal has to be to do so with minimal drag. Using proper wings makes lift production very efficient, and the cross section of the fuselage will not have much influence here. As a slender body the fuselage produces lift mostly where its width increases, regardless of cross section shape.

I am not thinking of a blended wing design, more like a flat bottom and a curved upper surface, maybe some splines on the side. I aim to fit it in the same profile as a conventional cylinder. Also, can you please clarify on why producing lift is trivial? The way I see it, a pure cylinder can be Aerodynamically optimised such that it produce more lift, less drag, and the internal volume is not less than 90% of a cylindrical profile.

@Peter Kämpf the aeroshell and the cylinder containing the rocket fuel are normally not the same. If it were, you would see an racetrack containing conduits for ignition and actuators, like you see on big rockets (like the Falcon 9). I would therefore put this down as an "argument" rather then an reason... With your permission I would extend my answer with this "argument"

Aren't cruise missiles generally launched vertically (unlike torpedos)? Or are you saying they repurpose torpedo tubes as vertical launch tubes?

@johnDanger: There are submarines with dedicated vertical missile launch systems, but there are also submarines where the torpedo tubes are the only way to launch something out of the boat.

@U_flow: Good point! No need to ask for permission, though.

@TonyStark At high dynamic pressure everything will produce ample lift. Now the goal has to be to do so with minimal drag. Using proper wings makes lift production very efficient, and the cross section of the fuselage will not have much influence here. As a slender body the fuselage produces lift mostly where its width increases, regardless of cross section shape.

@PeterKämpf I did not want to look like a copy cat :D.

I'm not happy with the very first part of your answer: can you please update it with the good point of @U_flow?

Actually, if I recall correctly, the big reasons for a cylindrical cross-section are that it has the highest volume to surface area ratio, which is good for reducing drag with the additional bonus that a cylindrical structure is very rigid and resilient to bending moments and torsion.

Yes! But X-15 had a cylinder, no area ruled fuselage, while SR-71 had the lower side shaped as a high speed boat, it seems generating some lift, besides the Reynolds number issues. Does a half cylinder shape, round side up, deserves testing vs a vulgar round fuselage? Me-262 fuselage was somehow a Rouleaux triangle, as Wankel engine Rotor. Did it generate lift? Blessings +

@Urquiola The SR-71 bottom was shaped to avoid horizontal radar reflections. Lift at supersonic speed is determined by angle of attack and at high Mach (>2) area ruling is no longer necessary. The fuselage shape has little influence; one configuration where shaping the bottom (of the wing and intakes, however) helped was the XB-70. The Me-262 fuselage was shaped to accommodate two turbojets F-80 style, but during engine development they grew in diameter so they had to be hung under the wings. Fuselage shape was kept to avoid lengthy redesign.

There are several reasons why most missiles have a round shape. I try to list (some of them) in roughly ascending order of importance:

Round shapes with wings are easy to calculate: Well known rough calculation methods exist which tell you which performance you can expect from a tubular shape at which you attach some wings. For example Missile Datcom is extensively used to calculate some performance numbers.

For the rocket engine, normally solid fuel is used. As the canister containing this fuel has to withstand the pressure of the rocket fuel while burning, a circular cross-section is optimal. However the aeroshell and the cylinder containing the rocket fuel are normally not the same. If it were, you would see an racetrack containing conduits for ignition and actuators, like you see on big rockets (like the Falcon 9).

Wings are efficient: Instead of going through the hazzle of designing, testing and manufacturing a complicated lifting body for which you probably still need wings, a tubular body is well tested and worked in the past. Wings are very well understood, and a lot of expertise exists to design these.

Wings can be deployed: You can unfold a wing, but you cannot unfold a lifting body. This is also important for my last argument.

A round shape is easy to manufacture: A tube with a pointy nose and some fins is easy and cheap to manufacture. As missiles are produced in fairly high numbers, ease of manufacture is therefore an important consideration.

A circular body is easy to be containerized into some launch/deployment canister. Missiles and similar weapons are often delivered in some canister out of which it is then deployed. The missile has to fit in this container. A circular cross-section is the most efficient way to put such a missile into this canister, as it has the least surface for the most amount of space (which also optimized aerodynamics). This containerization is also important for folding out wings and fins.

However all of these are only arguments for a circular crosssection. With the proliferation of modern CFD methods for example, it becomes much easier to design more complex shapes. More modern missile designs may feature quadratic or triangular shapes, e.g. the AGM-86 ALCM (Air Launched Cruise Missile) as pointed out by WPNSGuy.

For missiles which have to fitted in the rotary launcher of the B-52s, a more or less trapezoidal cross section is better, like for the AGM-86 ALCM

And some missiles are NOT cylindrical.
Here, 6x AGM-86 ALCM (Air Launched Cruise Missile) on a B-52 left wing pylon.

photo courtesy of NARA - https://nara.getarchive.net/media/technicians-check-the-left-wing-pylon-of-a-92nd-bomb-wing-b-52g-stratofortress-6d1f18

The Taurus KEPD 350 (another air-launched cruise missile) has a similar body shape.

What are we looking at here? Three missiles attached to a support? Two? Or is the whole thing one missile?

@WaterMolucule - That's actually 6x missiles. 3 front and 3 behind. Mounted on a B-52 wing pylon.

Note that these missiles were designed for fitting 8 on a rotary launcher in the bomb bay. That's the main reason for the body shape, another shape wouldn't fit that number in the bomb bay so this one maximises the number of missiles that can be carried internally. This was especially important for the B-1 as it was initially designed for internal weapons only.

Another factor:  Missiles need a nice, smooth skin for aerodynamic reasons.  You use less skin to contain a round missile than you use to contain a non-round missile.  Thus the round missile flies a bit further than the otherwise-identical non-round missile.

Missiles are essentially rockets, and rockets don't have lifting surfaces for the simple reason that they don't need to generate lift, because the thrust that their engine(s) produce is more than able to overcome both gravity and aerodynamic drag.

Both types of missiles mentioned by the OP (Tomahawk and Harpoon) have lift-generating wings. It's simply not true that rockets categorically don't have lifting surfaces, or that they cannot benefit from lift.

Some rockets/missiles are expected to follow a ballistic trajectory, so don't need wings. The remainder are intended to 'fly', but that is not directly connected to the propulsion type. The Space Shuttle was a rocket, and is a classic example of a rocket-with-wings.

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Why can't I ever get my right ear to pop on descent in a plane?
Whenever I'm flying, there's a period of descent where my right ear just refuses to pop. This has been bothering me for at least ten years.
There seems to be a long stage of descent where my ear is just in agony. I've tried chewing gum, closing my nose and lightly blowing, opening my mouth, everything. However, when descending into landing (I can see cars at this point) it will start to pop.
Otherwise, it'll pop when I swallow at this stage or even while I'm walking around in the airport. The only thing that makes it pop early and at the same time as my left ear would be when I yawn.
When it does pop, it actually hurts sometimes. It has a very distinct pop, too. Instead of a light pop, it sort of stutters a bit, like it pops twice, and it's much louder.
This phenomenon seems to be very unique to when I'm flying on a commercial airline and descending. It has never happened upon ascension, and from the few times I've driven into mountains it hasn't happened, although that hasn't happened enough to be sure.
What about the descent makes this happen? Is there anything I can do to fix this issue?

"closing my nose and lightly blowing" Actually it takes quite a bit of effort to pop your ears this way. Try blowing harder (and yes, it is uncomfortable).

This is too sideways a response for a proper answer, but if you take up scuba diving, you will find that you pop your ears automatically before any large pressure differential builds up.  That's good because the larger the differential, the harder it can be to pop them.  When ascending or descending in scuba, you have to pop your ears so frequently that it becomes an automatic reflex that you don't even think about.

I agree with John K that you should see a doctor if it’s much of a problem for you. Eustachian tube blockage is a very common problem. Yawning is the normal way of opening up the tubes, but there are a variety of different methods. They’re outlined in this Wikipedia page.

@WayneConrad you have to "manually" equalize as pressure increases (on the way down) but when surfacing your ears should self-equalize ... if you don't you end up with a nasty thing called a Reverse Ear Block - https://www.diversalertnetwork.org/health/ears/middle-ear-barotrauma-on-ascent

@ivanivan Thanks for the clarification.  I haven't dove for so long that I've forgotten the details.  But I still have the ear pop reflex I learned from it.

@WayneConrad haven't been "at depth" since the late 80s either... 2 very bad reverse ear blocks ended diving for me, both fortunately in relatively shallow water with plenty of support around. Had just finished my cave certs, rescue and recovery certs, and was working on my instructor certification... a friend's father is a flight surgeon and he told me to just hang it up.... the meds he offered didn't prevent the second block, and there really weren't any other options...  fortunately no issues when flying (pressurized cabin or open air)

The eustachian tube is a vent line that connects your inner ear to the back of your throat. Like the sinuses, higher pressure air flows outbound from the inner ear (when cabin pressure is dropping) with pressure changes easier than inbound (when cabin pressure is rising).
So the air trying to get back in on descent has a harder time than when it was leaking out unnoticeably on the climb, and a pressure differential builds up before it equalizes the pressure - the pop.  Part of the tube is through cartilage and it's helped to open more by mechanically "massaging" it so to speak by moving your jaw.
It sounds like the tube for your right ear, which is partly in cartilage and partly in bone, is misshapen enough that it takes an abnormally high pressure differential to equalize pressure when the pressure change happens quickly like on an airplane.  This is putting a lot of stress on your eardrum (which is what the pain is from).
Decongestants often help but if it is a severe chronic problem, which yours sounds like, as a last resort there is a procedure that is usually done temporarily on babies (where the tube is blocked until they grow more - one of my kids had one put in, which falls out on its own later), called a shunt, where a doctor implants a tube across your ear drum to allow the inner ear to vent that way.
Anyway, you should see a doc about it if it's that bad.


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When wiil this person be able to replace his engines on a bunch of smaller ones to attach them on clothes?
That is the real question that bothered me.
 UK 'Iron Man' suit

Turbojet, yes but why, no you don't need to cooler.

From the outlet cowling and nozzle, it they look to me like 6 standard RC jet engines (JetCat or so; JETCAT P200RX, for instance, has about 50 lbs of thrust, so in the right order of magnitude).
I don't think there would be any benefit whatsoever to using many miniature engines.

It certainly looks like some form of jet engines, probably turbojets as they are simpler and have better thrust to weight and thrust to size ratios than turbofans (though you pay for it in fuel consumption).
In general small engines perform worse than larger ones, so it pays to keep your engine counts to a minimum.

If using small engines, fans/propellers could do it. You would have to mount them on a frame though.

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If I buy my own aircraft in which to earn my PPL, does my instructor need to be certified to fly the type of aircraft I own/am training in?
It seems the most cost-effective way to earn my PPL is to purchase my own plane (with the intention to keep it for quite some time). I believe I would therefore need to find a CFI that is certified for that aircraft type, correct?

Welcome to aviation. SE! Are you asking about the US, or another country? Apart from certification, insurance is very important in this situation. Make sure you and your CFI are both covered. The insurance company might require the CFI to have some number of hours in the specific model of aircraft, regardless of what the FAA (or other regulator) requires.

Thank you, I didn’t think of the insurance requirement, will have to look into it. And I’m asking about the US.

FWIW, you have done the research and sums to back up your intuition about cost-effectiveness? Remember that buying the airplane is just the first cost. Then you need ongoing hangerage, maintenance, insurance... Not saying it isn't worth doing if you're flying-mad, but I'm not sure it's cost effective. In any case, good luck with your lessons! Happy flying.

I question the wisdom of learning to fly using an instructor not qualified for the equipment you're trying to learn on.  They probably are not familiar with best practices, emergency procedures, etc.  You don't want to end up in an emergency situation up in the air, and the instructor not having any experience in that scenario.

You are sort of correct. For the ground instruction for your basic Private Pilot Certificate, it would not really matter. For the actual flight instruction, the CFI has to be certificated for the category and class of aircraft in which you are being trained by them. If the aircraft is a taildragger, high performance, and/or complex aircraft, the CFI will need an endorsement in their logbook from another CFI showing that they have been trained for that scenario. If the aircraft requires a type rating (which almost no trainer aircraft does), the CFI will need a type rating on their certificate in that aircraft as well. Those aircraft requiring a type rating are generally defined by the FAA as:

(7) Aircraft type ratings—
(i) Large aircraft other than lighter-than-air.
(ii) Turbojet-powered airplanes.
(iii) Other aircraft type ratings specified by the Administrator through the aircraft type certification procedures.

Remember, the above explanation applies to the instructor’s Pilot Certificate for them to have the privileges to act as PIC while flying. The instructor’s CFI certificate is a separate certificate allowing them the basic privileges of instructing. The categories and classes listed on a CFI certificate are a little more general than those listed on a Pilot Certificate. An instructor will need both certificates to give the actual flight instruction in flight in the air. Ground instruction is different.
Most people learn to fly in something along the likes of a Cessna 150, 152, 172, 177, or (in some rare cases) 182. The Piper Cherokee line is another popular trainer. Even Cirrus has a line of aircraft that are very suitable as trainers. Any aircraft around that size or smaller is a great start.
As long as the CFI has an ASEL (Aircraft Single Engine Land) class rating on their Pilot Certificate and an ASE (Aircraft Single Engine) rating on their CFI certificate, they can instruct you in almost all aircraft typically used as trainers. If the aircraft in which you want to train is a float plane, the instructor will need an ASES (Aircraft Single Engine Sea) class rating on their Pilot Certificate. If the aircraft is a multi-engine, the CFI will need a multi-engine class rating (AMEL or AMES) as well as have a Multi-Engine Instructor certificate. If the aircraft is a rotorcraft, that falls into a different category than the above aircraft. Gliders also fall into a totally different category. So do balloons.
One caveat is that some CFIs are limited to training students for the Sports Pilot Certificate, only. While a regular CFI can train students for the Sport Pilot Certificate, a Sport Pilot CFI can not train students for the Private Pilot Certificate. Although the hours acquired in one can apply to the other in the same category and class, the Sport Pilot CFI can only endorse students for that specific test and checkride.
For a more in depth description of aircraft category, class, and type ratings as they apply to pilot certificates, please see Title 14 of the Code of Federal Regulations (14 CFR a.k.a. the FAR/AIM) Part 61.5. Especially pay attention to Subpart (c) pasted below.

(c) The following ratings are placed on a flight instructor certificate when an applicant satisfactorily accomplishes the training and certification requirements for the rating sought:
(1) Aircraft category ratings—
(i) Airplane.
(ii) Rotorcraft.
(iii) Glider.
(iv) Powered-lift.
(2) Airplane class ratings—
(i) Single-engine.
(ii) Multiengine.
(3) Rotorcraft class ratings—
(i) Helicopter.
(ii) Gyroplane.
(4) Instrument ratings—
(i) Instrument—Airplane.
(ii) Instrument—Helicopter.
(iii) Instrument—Powered-lift.
(5) Sport pilot rating.

How does the first CFI get theirs if they need a note from another CFI? I think I'm missing something simple here.

@Mast - They go to a CFI who already has the endorsement. In order for any pilot to get an endorsement to act as PIC in any complex, taildragger, or high-performance aircraft, they must receive both ground and flight instruction in that type of aircraft from a CFI who already has an endorsement for that type of aircraft. The endorsement is for a specific type, not for a specific tailnumber. This includes pilots acting as CFIs. This endorsement goes in their logbook, not on their instructor’s certificate. See 14 CFR Part 61.31.

@Mast - PS. An endorsement is more than just a note from a CFI. An endorsement is a granting of certain privileges and limitations that become a legal permanent record in the eyes of the FAA once granted by a designated legal representative. That is why a logbook is so precious to a pilot. Some endorsements are recorded nowhere else. In case of an accident, incident, or ramp check, the endorsement in the logbook is the only proof of having the authority to act as PIC in certain situations.

While the aircraft that you buy could conceivably require your CFI to possess certain additional ratings, such as if you purchase a twin-engine plane or a jet, most smaller, single-engine, prop planes will be covered under your CFI’s Single Engine Land (SEL) rating.

Yes, but.
With one notable exception, for any pilot to legally fly an aircraft, they must be rated for that category and class of aircraft. Some (generally larger) types of aircraft also require a type rating.
So, if you purchased a Cessna 172 (a very common primary trainer), your CFI would need to be rated for Airplane category, Single Engine Land class (referred to as ASEL). Like most small aircraft, no type rating is required.
Where the notable exception comes in is that a CFI can endorse another pilot (including a student pilot, like you) to solo in a specific type of plane. This allows you to complete the required solo hours before you can take the test to get rated for real.
One thing the other answers didn’t address is insurance. Your insurer may have additional requirements beyond the legal minimum, either to determine your rates or decide whether they will issue a policy at all. For instance, they typically ask the “total time” and “time in type” for each pilot on the policy, which will include your CFI. If your CFI doesn’t have enough (or any!) time in type, they may need to first get a few hours of instruction from someone who does before the insurer will let them teach you. So, if your plane is not a common one, it is probably best to check with a “type club” to find a CFI near you who already had the required experience.


text:
Do any airports have a steeper standard approach than London City?
Watching the CS100 certification of the 5.5deg steep approach into London City, I wondered if there were any airports with steeper standard approaches. By standard I mean published.

I have seen very steep non-standard approaches, but this is not the point of this question.

When I was living in Miami and had a relative typing flight plans for the FAA there, the airport at Tegucigalpa, Honduras, was notoriously the one where the passengers were most apt to be sharing an experience otherwise familiar only to dive bombers.

I'm a bit late to the conversation, but I think I have a winner so far, at 9.61° for the KASE VOR/DME-C approach.

Great find, even if late to the game!

I found the RNAV approach to Steamboat Springs at 7.75°

You win for steepest approach. Note, though, it only allows cat A and B aircraft.

@TomMcW True enough, so far. The runway is 450ft shorter than London City but it's the weight limit that is the disqualifier.

Wow that is a steep approach!

One of the steepest approaches within the CONUS is the LOC/DME approach to Aspen, CO, which has a final approach segment with a recommended approach glideslope of 6.59°.

Lugano LUG/LSZA has an approach  of 6.65°.
[][12]

Just came back from a backpacking trip into Lake Placid KLKP, glide slope 7.92, and the relics of the olympic ski jumps looming a 1/2 mile to the S of the runway which are to be avoided on the missed approach....which we were.


text:
Why would an F-35 take off with air brakes behind the cockpit extended?
At the Farnborough Airshow, I saw an F-35 take off with air brake behind the cockpit extended. Why would they do that?

Which model? A, B or C?

That is not the air brake, but the cover for the vertical air intake on the F-35B model, which is operated by the RAF.

To be clear, what OP saw is the cover in the open position, to enable the vertical take off.

https://www.youtube.com/watch?v=FaNPD3wIvAQ

I've added an image, but note that the shape and position of the cover on the actual plane is different from the one shown.

The airbrake is not a single piece on the F35, like the F15 have. That is just a fan cover for the F35 hovering variant. For airbrake, the F35 use the rudders, flaps and ailerons all at the same time.

Not an expert on F-35 or whether it would make aerodynamic or even structural sense, but to add to what others have said, a typical air break is designed to hinder horizontal movement by means of increased drag.
If your goal is a steep vertical take-off, such as some F35 models are capable of doing, then applying an air break could possibly be harmless or perhaps even beneficial by reducing the horizontal movement during the procedure (at least when the winds are calm).

An air brake will slow an aircraft relative to the airspeed, and not the ground speed. Additionally, the deceleration caused by an air brake is weakens as the velocity differential drops. Due to these two factors, the effect you are talking about is not very useful.


text:
How easy is it to pull the ejection handle in a Rafale B?
A civilian passenger ejected from a two-seat Rafale B during takeoff on Mar 20 2019. The investigation is underway as to how it happened, but one of the possibilities discussed is that the passenger accidentally pulled the ejection handle.
Having sat in various military aircraft over the years, I never thought it would be easy to accidentally pull the eject handle.
Is the ejection handle on a Rafale B easier to pull than most fighter jets, or closer to the hands' resting position?

The official report on the matter: https://www.documentcloud.org/documents/6836894-FRENCH-AIR-INVESTIGATION-REPORT.html

Believe I remember reading in Scott O'Grady's book that the pull handle in the F-16 required 35lbs of pressure, which he considered to be a lot, but how easy he found it to pull when the time actually came. That I think is the ACES II system, where the Rafale is an MB MK16 one. I would guess the pressures are pretty universal.

There's a little light reading about ejection seats, though no specs on the pull pressure required.  Also has a ton of info. Little clunky to navigate, but good.
As to how a civilian could pull a handle accidentally... I guess throw someone into a jet, pull a half dozen Gs and watch them grab for something. Most tandem aircraft have split ejection "options", for lack of a better term, meaning the RIO/FO/passenger can punch himself out, but leave the pilot inside. Gotta be a hell of a surprise when the back seater disappears like that.
Likewise, I've seen and heard of numerous cases of canopies being blown accidentally without an actual ejection. Had an F-15C I was working on do it one afternoon in FL.

I've dropped in an image from the martin baker site. Thanks for the link.

There´s a good writeup about an F-14 (acting) RIO who ejected himself because the handle was the first thing grabbed when the pilot went inverted. The backseater was military too, just wasn´t used to flying and the maneuver caught him not knowing what to do.

For reference, in this case; the rafale fleet is grounded because the ejection was setup to eject both, but the pilot was not ejected.

@RoryAlsop I've corrected the image; yours was the one for the Eurofighter instead of the Rafale.


text:
How does the Space Shuttle slow down during re-entry, descent, and landing?
Yesterday, my little brother asked me to help him build his new Space Shuttle Lego set.

When we finally finished building it, he started to play with his new toy and asked me to be the "Mission Control". After some time playing, he told me that he had to re-entry and land, so I gave him "permission to re-entry". Then he started to play as if he was coming back to Earth and told me that the Space Shuttle was too hot and moving too fast to land. And that got me thinking:

How does the Space Shuttle reduce speed during the re-entry process?
Does the Space Shuttle have flaps, spoilers and reverse thrust capabilities?
Can the Space Shuttle make a go-around?
Where does it land?

I know that when it is on the ground the Space Shuttle can deploy parachutes to reduce speed.

Are you talking about getting out of orbit and back into the atmosphere, slowing down from suborbital speed to landing speed in the atmosphere, or both?

I'm interested in the whole landing process from out of the orbit to the ground.

The Space Shuttle was a glider after re-entry so no reverse thrust and no go around.

Not entirely true, @Simon. It uses reverse thrust to deorbit, though that might be considered a technicality. :)

@Freeman Technically speaking it's a "retrograde burn"... something I definitely DON'T want to experience in an aircraft during Landing :)

@FreeMan it's not reverse thrust; it's ordinary "forward" thrust, while pointing the other way. Same result, different execution. At any rate, Simon did specify after re-entry, and the deorbit burn was definitely before re-entry. Pointing backwards whilst within atmosphere would be... inadvisable.

@FreeMan That's why I said "after re-entry".

Ah, yes, I did miss the after re-entry part. Point well taken.

To explicitly answer the title question: the de-orbit burn slows it down enough to de-orbit, then aerodynamic drag provides the remainder of the (backwards) acceleration, at least until touchdown where the wheels, wheel brakes, and chute also come into play.

Per Gabriel's comments, I've updated the question title to reflect the fact that he's asking about all phases from de-orbit to landing. While I agree that the re-entry itself is technically off topic here, the remainder of the descent and landing seems like it should be on-topic.

@reirab: I believe most of, if not all, the answer regarding the aerodynamic energy management is contained in the TAEM (Terminal Area Energy Management) details.

Your third question is answered by If the Space Shuttle missed its landing approach, what could have been done? on [space.se].

If you're interested in a more visual, and less technical, explanation of Space Shuttle reentry and landing, I gave a talk titled How to Land the Space Shuttle... from Space at the Stack Overflow meetup in October 2016.

I didn't notice this question until a couple of days ago, but as someone with an unhealthy obsession with specifically the entry and landing phases of shuttle flights, I can say there is a lot of factually incorrect information in the other answers here. Let me see if I can explain it better.
First, the two easy questions, which were answered well by other questions, but I'll include here as well for completeness:

Could the shuttle perform a go-around? No. The OMS engines are too weak to make a difference in the atmosphere, and the main engines (which would be powerful enough) are only fueled by the orange external tank which is jettisoned after launch.
Where did it land? 78 missions landed at the Kennedy Space Center, 54 (including the first) at Edwards Air Force Base, and 1 at White Sands. There were other landing sites designated for emergencies, but none were ever used.

Now, for the really big question of how the shuttle reentered and landed.

The primary source I'm going to cite in this answer is the Entry, TAEM, and Approach/Landing Guidance Workbook 21002 which was a workbook used for training astronauts. Sadly, I don't have a link to it, but it can be obtained from nasaspaceflight.com via an L2 subscription if you're really interested. I'm going to abreviate this source as ETAGW.

Orbital Mechanics
First, a real quick lesson in orbital mechanics. In order to change the altitude of your orbit you make a change in velocity ($\Delta v$). If you increase velocity, you'll increase altitude, and if you decrease velocity, you'll decrease altitude. However, this effect is most pronounced 180° from the position where you made the change. After a complete 360° orbit, you'll be at approximately the same altitude you started at.
This illustrates the effect:

Starting from the circular orbit (black), if you slow down at point A, you might end up with something like the red orbit, and if you speed up you might end up with something like the blue orbit.
Deorbit Burn
Because of the nature of orbital mechanics, as described above, you want to perform your deorbit maneuver on the opposite side of the planet from your intended landing site. This typically occurred over the Indian Ocean for a landing at Kennedy Space Center in Florida.
The burn itself was performed with the shuttle flying tail first and white (top) side facing towards the Earth (heat shield/black side facing towards space). The two OMS (orbital maneuvering system) engines were used to accomplish the required $\Delta v$ (anywhere between 200 and 550 ft/sec depending on the starting altitude). The burn typically took around 2.5 to 3 minutes. This would lower the perigee (lowest point in an orbit around Earth) to within a few miles of the ground (having a hard time finding a source, but I seem to remember it being around 30-40 miles), which was enough to ensure the orbital path would take them into thick atmosphere.
 Image Source
The OMS engines are essentially larger versions of RCS (reaction control system) jets. RCS jets were used for rotation (attitude) and small translation (velocity in a given direction) changes. The OMS were used for making orbital changes.
Both systems burned the same hypergolic mixture (monomethylhydrazine (MMH) and dinitrogen tetroxide (N2O4)). If the OMS had failed, the RCS jets could have, in theory, been used to slow the shuttle enough for reentry.
Nose Flip
Some answers have said that the orbiter would pitch down 140° for the flip. This is incorrect. After the deorbit maneuver was completed, the orbiter would pitch up about 220° until it reached a 40° nose-up angle of attack (referred to as the "EI -5 attitude" because they must be in that attitude by at least five minutes prior to entry interface).
They have about 20 minutes between the deorbit burn and EI-5, so there's plenty of time to pitch in either direction. Nose up was likely preferred because the APU exhaust vents point up near the tail. This naturally causes the orbiter to want to pitch up when the APUs are running.
During this pitch-up, they would fire the forward RCS jets to dump all the forward fuel, unless it was required for center-of-gravity reasons. The forward RCS jets weren't used during reentry, and dumping the fuel reduces potential hazards to the astronauts.
Once in position, open-loop entry guidance would begin, holding the orbiter at 0° roll (wings level), 0° yaw, and 40° angle of attack (alpha).
Entry Interface
NASA defines the entry-interface (EI) as an altitude of 400,000 feet. There's no hard-edge to the atmosphere, but this is around the altitude where its effects start to become directly detectable.
S-Turns
Some answers have claimed that the shuttle used S-turns for the purpose of slowing down. This is a very common, but over-simplified and arguably inaccurate, explanation.

"The next time you hear someone talk about the shuttle doing roll reversals to bleed off energy, do not listen. The shuttle does roll reversals because it has a very small alpha envelope." - ETAGW 2.8.1 (emphasis is from original source)

As with any airplane, the shuttle's wings generate lift. As the atmosphere gets denser, the wings are going to generate more lift, and this upward lift will cause the descent rate to slow. In fact if the shuttle maintained a wings-level attitude, it would eventually start to gain altitude causing it to "skip" across the atmosphere several times until it was slow enough to fall through. And while technically a skipping reentry would be possible, it would be very difficult to control with any precision.
So, instead, when the decent rate starts to slow, the shuttle goes into a bank. By controlling the bank angle, they're able to control how much upward lift the wings are generating, and, by extension, control their descent rate.

ETAGW Figure 2-5 illustrating lift vector.
Or course, with the lift vector pointed sideways instead of upwards, the shuttle is going to start to turn. Due to the incredible speed, the turn radius is enormous, but it does gradually turn nonetheless, and the orbiter develops an azimuth error (the difference between the orbiter's current direction and the direction to the landing site).

ETAGW Figure 2-3 illustrating azimuth error.
To correct this azimuth error ($\Delta z$), the orbiter performs "roll reversals". In other words, it turns in the other direction. These turns create the distinctive S-turn reentry track.
The first reversal always occurs at 10.5° $\Delta z$. Subsequent reversals occur at 17.5° until Mach 4 when it starts ramping down to 10° at Mach 3.

Note: all mach numbers given anywhere in this answer, or referenced anywhere in Space Shuttle materials, aren't true mach numbers. NASA uses 1000 ft/sec as an approximation of Mach 1, and all mach numbers are multiples of that velocity.

Ranging
Obviously, the ultimate goal of reentry is to reach your intended runway at an appropriate speed for landing. While the orbiter doesn't have any engines to help accomplish this, it does have a tremendous amount of orbital energy. Therefore the goal becomes energy management, and more specifically, drag management.
The orbiter has two ways to affect drag during entry: changing angle of attack (alpha), and changing bank angle.
Angle of attack is the quickest way to increase or decrease drag, but the orbiter was only allowed to deviate ±3° from the nominal alpha (40° for most of entry). This is the "very small alpha envelope" referred to earlier. The limitation is designed to ensure proper heat protection and maintain vehicle control.
Changing bank angle, as described above, allows you to control your descent rate. A steeper bank angle will result in reaching thicker air faster, and will therefore result in increased drag. A shallower bank angle will keep the orbiter in thinner air for longer, and result in less drag. However, it takes a little longer to see the effect of a bank change than an alpha change.
There are also bank angle limitations because, again, you don't want to skip out of the atmosphere, and you don't want to fall into thick air so fast that it exceeds the maximum drag the vehicle can handle, but it is a larger envelope than the alpha limits. In fact, in early stages of entry, the orbiter could have even flown upside down (with its lift vector pointed towards Earth) if necessary due to an under-burn as the result of a malfunction during the deorbit burn.
Entry Guidance Phases
I'm not going to go into detail about entry guidance, but I will say that the primary considerations change as speed and altitude changes, and the entry guidance is broken up into phases to reflect this.

ETAGW
In the chart above, the middle line represents the nominal profile. The lowest line is the "equilibrium glide" profile which is the minimum amount of drag that the orbiter must maintain to avoid gaining altitude and skipping. The line at the top left represents a thermal limit (if the orbiter exceeds it, it might burn up). The line at the upper right represents a dynamic pressure limit (if the orbiter exceeds it, it might break up due to aerodynamic forces).

Preentry: This is considered open-loop guidance because all it does it maintain 0° yaw, 0° roll, and 40° alpha until the total load factor becomes 0.132g (approximately 3 ft/sec2 of drag), at which point closed-loop guidance begins.
Temperature Control: Begins at closed loop guidance and ends at a velocity of Mach 19. Tries to maintain a constant temperature within the design limits of the orbiter.
Equilibrium Glide: Simply provides a bridge between temperature control and constant drag phases. It ends when drag reaches 33 ft/sec2. It's named as such because its shape is similar to that of the equilibrium glide profile.
Constant Drag: Maintains a constant drag rate of 33 ft/sec2 until velocity reaches Mach 10.5.
Transition: Designed to transition from the high drag and high alpha of entry to the lower drag and lower alpha required for the orbiter to fly more like an airplane. This phase terminates at Mach 2.5 when TAEM begins.

TAEM
TAEM stands for Terminal Area Energy Management. The objective in this stage is to get the orbiter lined up with the runway with the correct amount of energy to make its final approach. Again, I'm not going to go into a ton of detail (feel free to ask other questions if you want), but here's the gist:
If all went well in the entry stage, TAEM will begin at about 82,000 feet and 60 nautical miles from the runway (intended ground track, not straight-line distance).
Whereas Entry guidance primarily uses bank angle to manage energy, TAEM primarily uses angle of attack. Below Mach 1, the speedbrake (a split rudder) also helps with energy management.

Source: NASA
Phases of TAEM:

S-Turn: Usually not required, but the shuttle will perform S-turns if it is too high on energy at the start of TAEM (too high, or too close to the runway).
Acquisition: Turns the orbiter towards a point of tangency on the heading alignment cone (HAC) and then flys wings-level until it intercepts the HAC. The tangency point is referred to as "waypoint 1" (WP1). During this phase, the orbiter slows to below Mach 1, at which point the commander takes CSS (control-stick steering), which is the closest thing the shuttle has to a "manual" mode.
Heading Alignment: Guides the orbiter around a virtual "cone" (see diagram below) until it is in alignment with the runway. It's not really a cone, mathematically speaking, but it's the easiest way to visualize it.
Prefinal: Establishes the orbiter on the outer glide slope.

ETAGW Figure 3-13 illustrating the HAC.
Approach and Landing
The final guidance phase is called "Approach and Landing". It begins when the orbiter is below 10,000 feet and established on the outer glide slope (OGS), but no later than 5000 feet regardless of glide slope.
The OGS was a 20° glide slope for "light" orbiters (gross weight less than 222,000 pounds) or 18° for "heavy" orbiters (by comparison, normal airplanes use a 3° glide slope). Heavy or light depended on what was in the payload bay. The nominal aim point for the OGS was 7500 feet short of the runway threshold, but there was also a "close-in" aim point at 6500 feet which was used in the event of a strong enough headwind.
The speed brake was used to maintain 300 KEAS (knots equivalent airspeed - it's effectively the same as indicated airspeed) on the OGS until 3000 feet, at which time it calculated how much speed brake should be required for landing, and moved to that position. It would re-calculate once more at 500 feet.
At 2000 feet, the orbiter would begin a "preflare" maneuver designed to transition from the OGS to the shallow 1.5° inner glide slope (IGS). This was accomplished with a circular pull-up followed by an exponential decay onto the IGS.

ETAGW Figure 4-8 illustrating the preflare geometry.
In reality, the IGS is not followed for long, and is more of a guide for making sure you cross the runway threshold on the proper trajectory and get into position to begin the final flare, which is essentially the same as a conventional landing flare in a normal aircraft, except that the shuttle lands at a much higher angle of attack (about 8°) due to its delta wings (more similar to Concorde).
Landing gear was deployed at 300 feet, and if you're interested in landing gear, I wrote a whole answer on landing gear deployment once.
The targeted touchdown point was 2500 feet down the runway at an airspeed of 195 knots for light orbiters, or 205 knots for heavy (within +5/-10 knots).
The drag chute (an addition made in the early 90's) would be deployed shortly after main gear touchdown, but not faster than 195 knots, and sometimes they would wait until nose gear touchdown if there was a crosswind. It would be jettisoned at 60 knots to ensure the chute attachment mechanism didn't hit and damage the main engines.
Control
(e.g. how was the shuttle able to make attitude changes?)
In early entry, the orbiter is still controlled like a spacecraft, using RCS jets to control attitude. As dynamic pressure (q-bar) increases, the aerodynamic surfaces begin to become active and the RCS jets shutdown as follows:

q-bar = 0.5 pounds/ft2 (psf), the elevons begin to act as trim.
q-bar = 2 psf, elevons begin to act as active control surfaces.
q-bar = 10 psf, RCS roll jets are disabled.
q-bar = 40 psf, RCS pitch jets are disabled.
Mach 10, the speedbrake opens on a pre-programmed schedule to act as pitch trim.
Mach 5, rudder becomes active, initially acting primarily as aileron trim.
Mach 1, RCS yaw jets are disabled.

Navigation
(e.g. how did the shuttle know where it was at?)
Navigation, in NASA terms, basically means knowing where you are (guidance answers the question "how do I get where I want to go?"). During entry, the shuttle primarily used inertial navigation units, which were aligned using a star tracker prior to the deorbit burn. As it got closer to the landing site it could also incorporate GPS and/or TACAN signals into the nav data. OV-105 (aka Space Shuttle Endeavor) had a three GPS units installed and no TACANs, whereas the other orbiters had three TACANs and one GPS unit.
On the HAC, anywhere from about 15k to 20k feet in altitude, the orbiter would pick up the microwave landing system (MLS), which acts sort of like a very high precision ILS. From this, they're able to determine their position with high precision and accuracy. Once acquired, this becomes the primary source of nav data for the remainder of the flight.
On landing videos, you can actually see exactly when they pick up MLS because the altitude tape goes from being sort of jerky, then jumps a little bit and becomes smooth. For example, watch here at about the 20k mark (altitude tape is the one on the right).
Below 5000 feet, the orbiter was also able to use a radar altimeter for altitude information.

That's probably more information than you were looking for, but if you have questions about things I didn't cover, or didn't go into enough detail on, feel free to ask separate questions for those.

That is a potentially unhealthy, yet very useful, amount of information!

I do agree this is a great amount of trustworthy research.

The procedure for the space shuttle for re-entering the earth's atmosphere is roughly as follows:

The shuttle is usually flying upside- down, with the vertical tail facing the earth and nose in the direction of flight.
The shuttle first de-orbits by turning 180$^{\circ}$ (in the yaw axis) and firing the thrusters, thus reducing speed, a procedure called retrofiring (or de-orbit burn).
Then, the shuttle 'flips' ~140$^{\circ}$ (in the pitch axis), so that it enters the atmosphere at around 40$^{\circ}$.
At this point, the atmosphere starts to thicken and the bottom of the space shuttle heats up. Due to the very high angle of attack, the shuttle generates a lot of drag, which helps in reducing speed.
Then, a series of steep 'S' shaped banking turns at up to 70$^{\circ}$ of bank are performed, while still maintaining the 40$^{\circ}$ angle of attack. This is done in order to reduce the speed.
After the completion of the final (banking) turn, the shuttle control is taken over by the commander (it is under pilot control till now), who 'flies' the shuttle (at a negative angle of attack before leveling off) and touches down on the runway.

Source: zlutykvet.cz
The flight control system of the shuttle consists of the following components:

Maneuvering engines
Elevons
Body Flaps
Split rudder (which acted as a speed brake).

Source: quest.arc.nasa.gov
There were no reverse thrusters. The shuttle usually landed at the Kennedy Space Center in Florida or its backup landing site at Edwards Air Force Base in California; Re-entry was a one way trip. There was no go-around as the space shuttle was essentially a very high-tech albeit inefficient glider during the reentry and landing sequence.
After touchdown, the pilot chute is deployed after a second, which opens the main (drag) chute, which slows the shuttle down. After the shuttle stops, the drag chute is jettisoned.

Source: spaceshuttleguide.com

I might add a comment on your number 5, though nobody here really addresses it.  The steep banks in particular are used to control the vertical component of the lift vector.  Without them, the shuttle will still reenter, but it will follow a 'skip reentry' profile, essentially bouncing off the upper atmosphere until it bleeds off a large amount of energy, then sinking like a rock, resulting in reentry heating and loads beyond design limits.  The bank angle is varied to control the rate of energy dissipation, and the banks are reversed to keep the cross range deviation from getting too large.

the shuttle will still reenter, but it will follow a 'skip reentry' profile, essentially bouncing off the upper atmosphere Are you sure? My reading from NASA's site (2nd quote in my answer) seems to indicate that the S turns are done once in the atmosphere to bleed speed. They strike me as aerodynamically controlled turns, not steering jet turns (3rd quote).

Excellent answer but you might make explicit that the OMS engines are not used in-atmosphere at all; they fire for the de-orbit only.

@FreeMan The shuttle didn't use aerosurfaces until fairly low in the atmosphere where the density was high enough for them to provide control authority.  It should be noted that the concept of "in" or "out" of the atmosphere is not well defined -- the density varies continuously from entry interface to the surface.  These were not "S-turns" per se -- they were banks to control the lift vector and, correspondingly, the rate of descent. The S is just a consequence of having to roll back over to correct crossrange drift.

"with the vertical tail facing the earth and nose in the direction of flight" Are you sure? http://space.stackexchange.com/a/12323/4703

The deorbit burn was actually (to me) surprisingly small. I asked about that on [space.se] in the question How could a 90 m/s delta-v be enough to commit the space shuttle to landing?.

@RussellBorogove The OMS engines are not used in atmosphere; the Reaction Control System is, till the aerodynamic surfaces become effective

@LightnessRacesinOrbit I'm not getting your point as I'm basically saying the same thing as in that answer

@aeroalias: You claim the shuttle flew nose first, whereas that answer claims it flew tail first. Not really seeing how that's "the same thing".

@LightnessRacesinOrbit NASA suggests that aeroalias is correct. "When it is time to return to Earth, the orbiter is rotated tail-first into the direction of travel to prepare for another firing of the orbital maneuvering system engines."

@reirab: Yet other sources quote NASA as saying the opposite. I am beginning to suspect that this is mission-dependent (ISS vs non-ISS missions) and/or singularly a post-Columbia thing (though that page does say "continue to").

A lot of things wrong here. The shuttle was never flown with a negative AoA. Bank angles in entry often exceeded 70°. S-turns aren't really to slow down. The flip maneuver was pitch up, not down. And a few other minor things. I've written a very detailed answer below.

To initiate the landing process, the shuttle executes a deorbit burn

When it is time to return to Earth, the orbiter is rotated tail-first into the direction of travel to prepare for another firing of the orbital maneuvering system engines. This firing is called the deorbit burn. Time of ignition (TIG) is usually about an hour before landing. The burn lasts three to four minutes and slows the shuttle enough to begin its descent.All quotes sourced from NASA

To reduce speed once in the atmosphere

To use up excess energy, the orbiter performs a series of four steep banks, rolling over as much as 80 degrees to one side or the other, to slow down. The series of banks gives the shuttle's track toward landing an appearance similar to an elongated letter "S."

To control the shuttle within the Earth's atmosphere

Early in reentry, the orbiter's orientation is controlled by the aft steering jets, part of the reaction control system. But during descent, the vehicle flies less like a spacecraft and more like an aircraft. Its aerosurfaces -- the wing flaps and rudder -- gradually become active as air pressure builds. As those surfaces become usable, the steering jets turn off automatically.

To make a go-around

During reentry and landing, the orbiter is not powered by engines. Instead, it flies like a high-tech glider, relying first on its steering jets and then its aerosurfaces to control the airflow around it. Emphasis mine

i.e. it's a glider, no go around available.
Where does it land:  On the ground, of course!More seriously,

The primary landing site for most shuttle missions was the Shuttle Landing Facility at Cape Canaveral
Edwards Air Force Base on the Rogers Dry Lake Runways was an alternate. Edwards was also the primary landing site for the first several (10 or more?) shuttle missions.

Other alternate landing sites included:

White Sands Missile Range (the only other site to be used)
Vandenberg Air Force Base
Lincoln Airport/Lincoln Air National Guard Base.
Other locations were emergency abort destinations for use before the shuttle left the Earth's atmosphere.

Source: http://science.howstuffworks.com/space-shuttle7.htm

When a mission is finished and the shuttle is halfway around the world from the landing site (Kennedy Space Center, Edwards Air Force Base), mission control gives the command to come home, which prompts the crew to:

Close the cargo bay doors. In most cases, they have been flying nose-first and upside down, so they then fire the RCS thrusters to turn the orbiter tail first.
Once the orbiter is tail first, the crew fires the OMS engines to slow the orbiter down and fall back to Earth; it will take about 25 minutes before the shuttle reaches the upper atmosphere.
During that time, the crew fires the RCS thrusters to pitch the orbiter over so that the bottom of the orbiter faces the atmosphere (about 40 degrees) and they are moving nose first again.
Finally, they burn leftover fuel from the forward RCS as a safety precaution because this area encounters the highest heat of re-entry.

What's happening here is that the speed with which the Shuttle is flying around the Earth, which is the speed that keeps it in orbit, is reduced by firing rockets in the opposite direction. Once the speed is reduced enough, the Shuttle starts to fall out of orbit and back to the Earth. It has not yet started to encounter a significant amount of atmosphere at step 4. above.

Because it is moving at about 17,000 mph (28,000 km/h), the orbiter hits air molecules and builds up heat from friction [sic] (approximately 3000 degrees F, or 1650 degrees C).

This is the next phase of "slowing down". At this point, keeping in mind step 4. above, the Shuttle has no fuel and no way to power itself. It is now a glider falling down from space. As the Shuttle starts to hit air molecules, compression of the air generates heat (moreso than the friction - an error in the quoted passage), which we can view as a transfer of energy from kinetic to thermal. The loss in kinetic energy is a reduction in the speed of the Shuttle, so the Shuttle is now slowing down to atmospheric speeds. It's a bit tricky because the Shuttle needs air to slow it down, but hitting too much air too fast could cause a rapid heat buildup and destroy the Shuttle. The correct angle of incidence with the atmosphere is key to controlling the rate of heating versus slowing. This is how all manned spacecraft have gone from orbital speed to atmospheric speed since the very first manned missions.

When re-entry is successful, the orbiter encounters the main air of the atmosphere and is able to fly like an airplane [sic]. The orbiter is designed from a lifting body design with swept back "delta" wings. With this design, the orbiter can generate lift with a small wing area. At this point, flight computers fly the orbiter. The orbiter makes a series of S-shaped, banking turns to slow its descent speed as it begins its final approach to the runway.

The orbiter is really a glider at this point, not an airplane. It does not have control surfaces as sophisticated as many airplanes do, so the S-turns are used to slow it down.

When the orbiter is 2,000 ft (610 m) above the ground, the commander pulls up the nose to slow the rate of descent. The pilot deploys the landing gear and the orbiter touches down. The commander brakes the orbiter and the speed brake on the vertical tail opens up. A parachute is deployed from the back to help stop the orbiter. The parachute and the speed brake on the tail increase the drag on the orbiter. The orbiter stops about midway to three-quarters of the way down the runway.

So while the Shuttle has an airbrake system in the tail, it is generally not used until after touchdown.
As noted elsewhere, there is no ability to go-around. Once the de-orbit burn is past a certain point, the re-entry and landing are fully committed. Given that fact, and the fact that the whole speed management process, line up for landing, flare, touchdown, and roll to a stop have to happen correctly the first time with not a very wide margin of error, we can be impressed at how we've never lost a Shuttle in the landing process, and only one Shuttle during re-entry.

Please note that air is heated mainly because of compression, not friction. This is a quite common misconception actually. See https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#Reentry_heating

@VladimirCravero Nice catch! I never knew that but it makes sense. I'll edit.

To give a less scientific version of what was already stated: there is no need to significantly reduce speed before re-entry as the re-entry is the way to reduce speed. And the Shuttle won't be hot before the re-entry, but rather the re-entry heats it up.
In some more detail: Yes, the Shuttle needs to slow down before landing. But the reason for its high speed is not that its falling down from such a high altitude. Rather, it's really not that high: AFAIK a typical Shuttle orbit is about 150km above ground. If you compare that to the diameter of Earth at more than 13000km, the Shuttle orbit is actually kind of close to the ground. The reason for its high speed (about 5 miles per second) relative to the ground is that it needs that velocity to stay in orbit and not fall down. That's why the Space Shuttle's sits on such a huge rocket on launch: it is necessary not so much to lift the Shuttle high up, but rather to give it that huge speed needed to stay in orbit.
But you can't land a Shuttle at that velocity, so the Shuttle needs to slow down before landing. How do you do it? Using another rocket booster would be an idea. But that would mean carrying huge amount of rocket fuel into orbit. And that in turn would require far bigger rockets at launch to lift and speed up the mass added to the Shuttle by those "brake" rockets. Instead, the Shuttle uses another approach: It is  slowed down only slightly (the "de-orbit burn" explained in other good answers) using its thrusters. This way it cannot maintain its orbit and gets closer to Earth and its atmosphere. The de-orbiting burn does not significantly reduce the Shuttle's velocity, but in the atmosphere its velocity causes significant drag. And its that drag on re-entry that at the same time slows down the Shuttle and heats up its hull.

The space shuttle slows during re-entry using its underside, flying at a very steep angle of attack.. Here are some images that illustrate what it looks like.  The re-entry generates a lot of heat and the underside has special heat-resistant tiles to cope with this.
During re-entry the shuttle isn't really 'flying' so much using its underside to slow down. At that stage the usual flaps, spoilers and  reverse thrust wouldn't do much. Re-entry refers normally only to the portion where the shuttle is coming into the atmosphere. After a while, when the speed is reduced sufficiently, the shuttle starts to fly more like a normal plane, and uses normal controls. That phase isn't normally called re-entry. When it has actually landed it has a parachute that slows it down, as well as normal wheel brakes, that help slow it down. The engines are nor working during landing, so there is no reverse thrust.
The shuttle has no way to make a go-around.
The shuttle usually lands at Kennedy Space Center, while early missions and some later ones landed at Edwards Air Force base in California. One missions landed at White Sands base in New Mexico. Wikipedia has more information

A quick glance at the Space Shuttle's page on Wikipedia will answer all your questions.
By the way, Space Shuttle (more specifically, the orbiter was (last flight was in 2011) no different from any other spaceship/capsule/orbital vehicle/etc.: during re-entry, aerodynamic drag was used to slow down the vehicle.
The Orbiter was a lifting body, with ailerons/elevators and a rudder that also worked as speedbrake.
The Orbiter was a "glider" during re-entry, with no propulsion, so a Go-Around was out of question.


text:
Why are Western helicopters more expensive, yet smaller in size, but Russian helicopters are way less expensive, and larger in size?
So, I was looking around for prices of the Bell 412, Blackhawk and Mil Mi 8/17 prices, and the Bell 412, despite being a lot smaller than the Mi8, was US$2mil more than the Mi8.

source for prices? New or used?

The cost of these types of aircraft is so much more than just the window sticker. Take into account getting it serviced (an Mi8 might be a good alternative to the Bell 412 if you are only operating it in Russia), spare parts, lead time, availability of service centers, etc. That Mi8 might be cheap, but try containerizing it and sending it to Russia for service every year or two...

There might also be some currency conversion & export factors to be considered, for much the same reason that it is (or was, last I looked) cheaper to buy former Soviet bloc jet fighters than US ones.

Everybody knows it costs more to make things smaller & lighter.

@Jpe61 multiple websites. Im generalising prices here.

Because they are of better quality than Russian helicopters?

labour and material cost for construction is quite a bit lower in Russia than it is in the west. Environmental regulations and other artificial means inflating the price tend to also be less there.

It's just market.
Like most markets, it's not even entirely rational. In the end, people may just have preferences. It commonly happens that a car X is cheaper than Y (and/or depreciates more), despite being better on every objective measure as a vehicle. But on the Y's side may be long-term reputation, familiarity, etc.
Still, there are many perfectly rational reasons for such disparity (lower cost of Russian aircraft), particularly in the West.

Service cost and, even more importantly, its availability. Russia is not particularly renown for its after-sales service, even within the country. A grounded aircraft is a big money drain.
Likewise, availability and cost of pilots for such less common aircraft. This includes training, licensing them etc.
Typically higher fuel consumption per unit payload (for the same generation of aircraft).
Typically smaller service intervals and shorter overall lifetime. This is partly due to military origin of most Soviet/Russian helicopters.
Depreciation and later sale prospects. This is somewhat a vicious circle, but it's an important factor affecting purchasing decision.

Since no one else has answered I would assume this is almost entirely down to regulator costs. Organisations like the FAA and EASA require so many independent tests and paperwork its probably harder in a "western" country to certify an aircraft than to design one. If you can find a Russian aircraft that meets western certification it should be more comparable in price to western aircraft.
You will likely find that non-Russian helicopters that are not certified for normal flight operations (ie. X-military, experimental), are comparable in price to similar Russian aircraft.

Mi-8 and Mi-17 are operated all over the world including western countries, so they are almost certainly certified just like the Bell ones.

Many (most?) of the ones I have scene are used exclusively for stuff like helicopter logging, those are often operated under less strict maintenance and inspection rules. I do not have personal experience with the exact rules they operate under.


text:
Is the Mil Mi-2 still in production?
I have read conflicting reports that this Russian helicopter is out of production, yet others say otherwise. Could anyone confirm?

For those reading this questions in few years, you may precise the current date into your question.

Both German and English Wiki say that the production of the Mi-2 ended in 1998. They refer to this russian document. Where did you get the information from that it is still in production?

@PerlDuck The russian document also says (Google translated to English): "In 2005, another 11 helicopters are planned to be manufactured for Indonesia.". The document only lists the total number of produced helicopters for the time from 1965 to 1998, but that does not necessarily mean production stopped then.

@Bianfable, it rather doesn't mean production resumed. You can safely discount any such 'plans' until you see that it actually happened.

Mi-2 was almost entirely produced in Poland, on PZL-Świdnik. That production officially ended in 1992.
Since then, a few new modifications/prototypes may have been produced, according to various sources, but they were almost certainly retrofits of the existing airframes.
In 2012, it was announced that production of a modernised Mi-2A would start in China, but I could not find any confirmation that it actually happened. Frankly, I see no good reason why it would. Generally, any announcement of plans from Russia in the last 30 years should be treated with extreme caution and not considered valid without confirmation.


text:
Does going from SPL with TMG to PPL(A) automatically give me a PPL(A) TMG rating?
I am currently training for PPL(A) while holding an SPL with TMG rating.
Since I have more than 24 hours on TMG, I only need 15 hours of flying to obtain the PPL(A) license according to the EASA Part FCL.
My question is: Will I automatically receive the TMG rating with my PPL(A) after my skilltest, or will my TMG rating only be associated with my SPL?
In my opinion, I would find it strange, if I was not allowed to use my TMG rating on my PPL(A), since I was taught to fly powered aircraft on a TMG.

In FAA land (so not an answer, but may be similar), you can only hold one level of pilot certificate at a time. In the above case, your SPL would be replaced by a PPL with ratings for both ASEL and GLI, but the GLI rating would be restricted to SPL privileges since you haven't passed the PPL test in a glider yet.


text:
How do I include a STAR in an ICAO flight plan?
Would it be in accordance with ICAO norms to include a STAR identification right after the airway name in the field 15 of the flight plan? Or should the connecting point between the airway and the STAR be included before the STAR?
Example without CP:

R460 LKN R594 JAL5E

Example with CP:

R460 LKN R594 JAL JAL5E


text:
What was the most efficient cruising altitude of the Lancaster bomber?
An earlier question concerning lower high altitude cruising fuel efficiency of the B-29 bombers with 4 x Wright R-3350 air-cooled radial Cyclone engines made me wonder about the Lancaster bomber, which was powered by 4 x Rolls-Royce Merlin liquid cooled in-line engines.
The R3350 needed to enrich its fuel mixture and open its draggy engine cowlings to avoid overheating its engines, negating the benefits of higher TAS with greater altitude.
Was the Lancaster able to avoid these issues with liquid cooling and gain fuel efficiency at higher altitudes, or would the extra demands of turbo and or supercharging limit these gains as well?
What was the Lancaster's best cruising altitude?

The Lancasters regularly cruised above 20,000 ft, near their service ceiling of 21,400 ft at 63,000 lbs. Nine model B.III's were converted to B.VI's by installing two-stage superchargers. This increased their service ceiling to 28,500 ft., but the engines were notoriously prone to failure for various reasons, including RPM "hunting" which would make it difficult to synchronize them. These aircraft were pulled from service in 1944.

This doesn't answer "What was the Lancaster's best cruising altitude?" as far as I can see.

It does. I think everyone who is a pilot knows there is no "best cruising altitude" because it's always a judgement called based on many factors such as load, weather, etc. The fact that they "regularly cruised above 20,000 ft" tells you the answer as it relates to operational activities. Different models could also cruise at higher altitudes, as I explained in my answer.


text:
What are the differences between the CH-46 and the CH-47?
The CH-46 and the CH-47 Chinook are very similar-looking aircraft and seem to serve similar purposes - only though for different branches of the U.S. military.

What are the differences between the CH-46 and the CH-47?
Why does the military run both instead of settling on one?

The military don't run both.  Where did you come up with that?  The V-22 replaced the Phrog.  (CH-46) for the Marines, and the CH-60S/MH-60S replased the CH-46 or the Navy Vertrep mission starting about 15 years ago.  Part of the problem was that it was going to cost about a billion dollars to restart the CH-46 line in Philadelphia back in the late 90's ... but that's another story.

Another of the issues leading to retirement is that the 46 airframe was apparently subject to a lot more fatigue issues than the 47. Everytime I flew in one it seemed the thing was trying to shake itself like a dog when the blades started turning. :) It would seem logical that the effort to overhaul airframes would cost so much money that it would be considered yet another reason to pursue a completely different aircraft as a replacement. The Osprey can also get to wherever it is going much faster than the 46, 47, or 60's. Big issue when having to deliver Marines in a hurry.

The difference is in mission, and the difference is non trivial.
The twin rotor configuration goes back to the 1960's. ("Flying banana" Piasecki H-21.  The CH-47 replaced it in Viet Nam in 1965).  Chinook became the Army's heavy tactical lift during Vietnam.  Like the C-130, that particular design is timeless.  The CH-47F is the current configuration.  It carries about twice as much as a CH-46 could.  It is also one of the faster helicopters there is (it can fly almost 200kts) though the CH-53E has flown faster.
The CH-46 was an adaptation of the same idea, but made smaller and marinized: it had to meet a host of Marine Corps and Navy requirements to fit on amphibious ships and supply ships. Space and fit are non-trivial limitations when writing requirements for naval aircraft.  (As an aside, the US military no longer operates the CH-46.  It appears that the last CH-46 squadron in the USMC, HMM 774, let go of its last Phrogs in 2015 and is now VMM 774, flying V-22's. The Navy Sundown for CH-46 was in 2004.)
Not having to take off some power for a tail rotor is an advantage.  The CH-46 mission for the Marine Corps was vertical assault (it carried more than a Huey and predecessors like the CH-34); for the Navy, it was the VERTREP mission.
The payload and maneuvering benefits from the lack of a tail rotor made the VERTREP mission a perfect fit for the CH-46.  One of the challenges in ship borne operations is the ability to run simultaneously resupply by air and ship-to-ship (UNREP) while not being operationally constrained (for the ship drivers) "getting into the wind."  That limitation tail rotor helicopters don't handle as well as the CH-46.  (That point was a core argument against CH-60S as replacement for  CH-46; but that's another matter).  I've flown VERTREP in helicopters with tail rotors; the CH-46 was less constrained than we were.
What about Marine and Navy Heavy Lift missions?
The Marine Heavy lift (analogue to the CH-47 for the Army and Air Force CSAR) is fulfilled with the CH-53, and has been for over 40 years.  The CH-53 can fold its tail to fit on a ship.  Even with folded blades, the Chinook's deck footprint is / was too large(at the time) on the amphibious ships in service.  The Navy VOD (heavy lift) was handled by CH-53's for 40 years.  They have since given that mission to the MH-53E minesweepers.  (Flexible, that's helicopters!)
Smart Requirement Writing led to smart choices
"The Military" would have made a significant mistake "to just make one type" since back in the 60s and 70s, making mission specific aircraft was the way to go.  Quite frankly, it makes for cheaper aircraft to build it for one core mission.  (See the A-10 as a fine example of that).
Note: An early failure in "one size fits all" was the F-111.  A current "one size fits all" example of cost going through the roof is F-35.
At the time the CH-46 and CH-47 were procured, the military was smart: apply the KISS principle to get aircraft that fit mission requirements.  The Army and Navy mission requirements were not identical.
(So how do I know all that?  25 years Navy pilot (helicopters, ASW warfare specialty, did other stuff like Vertrep ...), significant experience in multi-service operations, and a few years having to work in an acquisition job.)

Another example of the Navy being smart by not falling for congress' eternal attempt at a one size fits all piece of equipment is their refusal to buy the F-16 and navalise it, instead opting for the F/A-18.

Another example of "on size fits all" is the A400M that is currently replacing transport aircraft in europe.

@jwenting Yes, though that program got significant criticism from all and sundry until it went operational, though they did have to address the tail crack problem (IIRC, those stall fences on the tops of the wings mitigated the airflow problem).  Jost, A400M is early in its life, we'll see if, like many other programs, it works out the wrinkles.  (Remember the C-17 wing problems?  )

@KorvinStarmast yes, the F/A-18 wasn't smooth sailing but ended up being a superior platform to what the F-16 could ever have been in carrier service (it would have been severely overweight, underperforming even more than early F/A-18A models).

25 years in naval aviation and a few years in procurement...  There are some "why doesn't the military use x" questions hanging around on this site that I'd love to see your answers to.  Especially the U2 v SR-71 debate.  I know, different branch, but I figure you'd still be more informed on the subject than the answers we've had so far.

@JayCarr While I am familiar with SR-71, I only ever worked with U-2 operationally, and that for less than a year.  I'll take a look.

Isn't the main reason for the one-size-fits-all concept that it lowers development cost? Funny how that works (or doesn't).

@TomMcW That's the hypothesis, and a bit of wishful thinking that does not seem to have paid off in practice for aircraft.  For radios, maybe it works.

@KorvinStarmast "You can't fold a Chinook." Not quite accurate. The CH-47 can fold its blades for storage. The early models do it manually, the later models have an automated mechanism. The CH-46 had mechanically folding blades all the way back to the "A" models on which I worked. Quite a cleverly designed mechanism, by the way. :) Another big difference between the two is that the Chinook is only designed to be able to float on water for 30 minutes minimum. Frogs can float for as much as six hours.

@JuanJimenez OK, I'll update that.

They are run by different services- the CH-46 was operated by USN and USMC (before their retirement in 2015), while CH-47 is operated by the US Army and other foreign operators.
Both the aircraft look similar as their genesis lies in the same program. During 1950, the Vertol company started work on a medium lift helicopter, which led to the development of V-107, which the US army ordered as V-107. However, they later changed their requirements (they decided to use Hueys for tactical transport instead of V-107), leading to the larger and heavier V-114. While V-111 entered US army service as CH-47A Chinook, the smaller V-107 entered USMC service as CH-46A Sea Knight.
Though they look similar, they are in fact, quite different. CH-47 is much larger, has more powerful engines and has a substantially larger MTOW (22t for CH-47F as against 11t for CH-46E). Practically speaking, the helicopters are similar only in their tandem rotor configuration- otherwise they belong to separate weight classes.
Unlike CH-46, production is still running for CH-47.Coming to visual differences, the engine placement, landing gear and side sponsons are all different in both aircraft. globalsecurity.org has some details on this:

Differences between CH 47 and CH 46; images from globalsecurity.org

Besides all the above differences which are correct, we can also add a type of difference the fate of them. Marines decided to retire and replace the CH-46 with the Bell/Boeing MV-22B Osprey whilst the Navy did the same with their UH-46 by MH-60S and civilian Pumas.  The Army instead continue upgrading airframes as it has done since the 60s (upgrading A/B/C models to D, then D to F in the 90s) and nowadays is still fielding new build CH-47F-MYII blocks. This will assure the Chinnok a 100-year lifespan.

This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review

Got it ! thanks